# Homologous Series and Functional Groups

## A homologous series is a group of organic compounds that are arranged in order of increasing molecular weights, such that they differ from each other by a –CH2 (methylene) group. Each member of a homologous series is called a homologue. All the compounds in this series have similar chemical properties but they differ in their physical properties. Different members of a homologous series can be assigned the same general formula and can be prepared by the same method of preparation. An increase in molecular mass of members within a homologous series leads to a regular gradation in their physical properties. Knowledge of homologous series makes the study of organic compounds easier and systematic. A functional group is an atom or a group of atoms bonded to the carbon of the organic compound, which largely determines the structure and the properties of the organic compound. It is mainly responsible for the chemical properties or reactivity of organic compounds.

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• Q1

Marks:1

A= conc. KOH and B= aq. KOH

##### Explanation:

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• Q2

Identify the sixth member of the alkyne series.

Marks:1

Heptyne

##### Explanation:

First six members of alkyne family are;

Ethyne, propyne, butyne, pentyne, hexyne and heptyne.

So, sixth member is heptyne.

• Q3

The two successive members of a homologous series differs by:

Marks:1

14 amu

##### Explanation:

Each member of the homologous series differs from the preceding one by the addition of CH2 group and by 14 amu.

• Q4

Choose the incorrect statement from the following.

Marks:1

aldehydes contain CO functional group.

##### Explanation:

Aldehydes contain CHO functional group.

• Q5

An organic compound with molecular formula C3H8O can have functional groups:

Marks:1